This invention relates to the field of medicine, particularly to vascular surgery and neurosurgery. More specifically, this invention is intended for the occlusion (plugging) of the lumen of pathological vessels of the brain.
As is known, about 50 percent of arteriovenous aneurysms of the brain are inoperable. Part of them are subjected to the embolization of the afferent vessels feeding the aneurysm.
Contrast plastic or porcelain globules have been used of late for the purpose of embolization of the afferent vessels of cerebral aneurysms. Luessenhop, Spence and Washington (JAMA, 1960, 172, 11, 1153-1155). Kosary et al. (J. Neurosurgery, 1968, 28, 6, 605-608; Neurochirurg. 1971, 14, 3, 98-101).
However, the use of contrast globules is not devoid of disadvantages, among which one may note the necessity of opening the carotid artery for introducing the globules into its lumen; the placement of a vascular suture onto the carotid artery and sometimes its ligation; difficulty in selecting the globules for occluding the cerebral vessels; a globule with a diameter smaller than the vessel to be occluded may penetrate into the distal portions of the vessel, while a globule of a greater diameter may plug the vessel's more proximal portions.
A globule introduced into the lumen of the carotid artery is uncontrollable, and may inadvertently not plug the cerebral vessel intended for occlusion, but another, functionally more important, thereby causing serious cerebral complications, and in some cases causing lethal results.
Known in the art are devices for occluding (plugging) a blood vessel for a curative or diagnostic purpose (cf. U.S. Pat. No. 3,834,394; Cl. 128-325, accepted patent specification in Great Britain Pat. No. 1,333,096, 1973; Cl. A5R). We have taken as the prototype the occlusive device (bulb) according to U.S. Pat. No. 3,834,394.
The prior art device appears as a hollow elastic bulb, its distal and proximal ends being thicker and more elastic than the walls of its body. The proximal end of the bulb contains a canal for temporarily connecting the bulb's cavity with the bore of an internal catheter. The internal catheter lies within the bore of an external catheter. With the aid of this system of catheters the occlusive bulb is carried through a puncture in the wall of a trunk vessel to the required portion of the vessel to be occluded. The internal part of the canal of the bulb's proximal end has a one-way valve (normally closed), comprising a shutter whose plane is situated on the internal opening of the canal perpendicular to its longitudinal axis.
Fillers are introduced into the cavity of the occlusive bulb through the bore of the internal catheter for increasing the volume of the bulb to the size necessary for occluding the vessel. When necessary, contrast agents are introduced into the space formed by the external surface of the internal catheter and the internal surface of the external catheter. At the moment of detachment of the internal catheter from the occlusive bulb, the distal end of the external catheter is thrust against the proximal end of the bulb, thereby ensuring the fixation of the occlusive bulb at the site of the occlusion.
The design of the valve of the device known in the art precludes the withdrawal, when necessary of the filler from the bulb's cavity. It is therefore impossible to diminish the volume of the bulb. Nor does this permit changing a mistakenly chosen site of the occlusion, or the removal from the vessel of a bulb already dilated by the filler in case the patient reveals intolerence to the occlusion.
Besides, during the separation of the catheter from the bulb, inversion of the valve may occur, disrupting the reliable sealing of the bulb's cavity. As a result, the filler will escape from the bulb's cavity, causing spontaneous diminution of its volume and the bulb's travel with the blood flow with subsequent uncontrollable occlusion of vital vessels.
It is an object of the invention to provide an occlusive device which allows reliable plugging of small (0.5 to 0.25 mm) vessels of the brain.
Another object of the invention is to provide an occlusive device that can be drawn along convoluted and branching vessels of the brain.
Still another object of the invention is to provide an occlusive device that may be expanded by fillers to a volume 10-50 times greater than the initial volume of the bulb.
A further object of the invention is to provide an occlusive device whose valve reliably shuts off the bulb's cavity at its maximum volume and will not become inverted during the removal of the catheter from the bulb.
A further object of the invention is to provide an occlusive device capable of being expanded by any liquid fillers to which the patients organism is compatible.
Still another object of the invention is to provide an occlusive device whose connection with the catheter is sufficiently strong to preclude the bulb from being detached from the catheter by the blood flow.
The final object of this invention is to provide an occlusive device which dampens its own vibration due to the turbulent flow of the blood when the bulb is advanced towards the vessel to be occluded.